1. Field of the Invention
The present invention relates to a method for the surface treatment of an OLED (organic light emitting devices) panel, especially relates to a method for forming a photosensitive pixel-defining layer on an OLED panel.
2. Description of Related Art
Currently, OLED displays attract much attention of scientists and researchers because of several advantages such as light weight, high contrast, high response rate, low power consumption and high brightness. The conventional method for manufacturing OLED displays including forming parallel stripes of anodes, parallel ramparts of photoresists which intersect the parallel anodes, organic electroluminescent layers and cathodes on a substrate subsequently. The photoresist ramparts act as shadow masks for the formation of pixels when further vapor depositing organic electroluminescent materials and cathodes on the exposed anodes between photoresist ramparts. However, as the cathodes form on the organic electroluminescent media between photoresist ramparts, the separation or insulation between the cathodes and the anodes is not so ideal since the borders of the pixels are only roughly defined by the photoresist ramparts or by the anodes. In many cases, the cathode materials deposited on the sidewalls of the photoresist ramparts contact with the anodes on the substrate to cause shorts. Therefore, the stability of OLED displays and the yield of manufacturing OLED displays are often poor. The lifetime of OLED displays is not acceptable.
Recently, a suggestion for improving the drawback by forming an insulating layer of SiO2 between pixels and photoresist ramparts is proposed. However, the process for forming SiO2 insulation layer is very complicate and costs high. The formation of SiO2 layer for insulation is not suitable for the mass-production of OLED display panels. Another suggestion for exempting from these shorts by forming photoresist insulation layers between the anodes and the photoresist ramparts is proposed. However, since the photoresists release water or organic solvent vapor which will ruin the sensitive organic electroluminescent media in the OLED displays, the photoresist insulation layers are not the right answers to solve this problem. On the other hand, the photochemical stability of photoresist is low since there are many photosensitive chemicals in the photoresist compositions. Since the OLED display is operated under high brightness, the poor photochemical stability of the photorresist insulation layers does not result in durable insulation. Therefore, the lifetime of these OLED displays with photoresist insulation layer is not acceptable because of frequent high brightness of OLED displays.
Therefore, it is desirable to provide an improved method for manufacturing OLED panels to mitigate the aforementioned problems.